The present invention relates to a device for feeding liquid such as water, fuel or the like under pressure. The device for feeding liquid under pressure according to the invention is suitable particularly for a device for collecting condensate generated in a steam piping system at one time and sending the condensate to a boiler or some equipment utilizing waste heat.
Most of the condensate condensed and generated in the steam piping system still has a substantial amount of heat. For effective utilization of such energy, condensate recovering systems are widely used in which condensate is recovered using a device for feeding liquid under pressure and the condensate is sent to a boiler or some waste heat-utilizing equipment to effectively utilize the waste heat.
The liquid pressure-feeding device utilized in such a condensate recovering system functions to collect condensate in a sealed vessel at one time, introduce an operating high pressure fluid such as steam or the like into the sealed vessel by switching a change-over valve and forcibly discharge the condensate within the sealed vessel by the pressure of the operating fluid.
In order to operate the liquid pressure-feeding device at a high level of efficiency, it is necessary to accumulate as much condensate as possible in the sealed vessel and to switch the change-over valve to introduce the high pressure operating fluid just at the right time.
Accordingly, in most of the liquid pressure-feeding devices, snap mechanisms using coil springs have hitherto been generally employed to ensure the switching of the change-over valve. The liquid pressure-feeding device, in which a coil spring is used, is disclosed in U.S. Pat. No. 5,141,405.
FIG. 5 shows the main construction of a snap mechanism in the liquid pressure-feeding device having the inlet valve of its change-over valve in a closed state. The snap mechanism 100 is composed of a float arm 101, a sub-arm 102 and a compressed coil spring 103. The float arm 101 is fitted for oscillating motion to a support frame 105 with a pin 106, and a float 108 is secured to the front end of the float arm 101 at the opposite side.
The sub-arm 102 is connected at its one end to the support frame 105 for oscillating motion with the same pin 106 as the float arm 101 and is connected at the other end to one end of the coil spring 103 with a pin 110. To the center of the sub-arm 102 is connected a valve operating rod 111 with a pin 107. The valve operating rod 111 is connected to a change-over valve 120 shown in FIG. 6. In FIG. 6, the inlet valve is in an opening state. That is, an actuating rod 121 at the lower portion of the change-over valve 120 is connected to the valve operating rod 111. The actuating rod 121 and valve operating rod 111 may be one and the same member.
The change-over valve 120 comprises a gas inlet valve 122 and a gas outlet valve 123, which are opened and closed respectively, accompanying the upward movement of the valve operating rod 111. A ball-like gas inlet valve body 124 is disposed in the gas inlet valve 122 and a flat plate-like gas outlet valve body 125 is disposed in the gas outlet valve 123, said valve bodies being connected to the actuating rod 121.
Referring to FIG. 5, the end of the coil spring 103 remote from the sub-arm 102 is connected to the float arm 101 with a pin 112. In the liquid pressure-feeding device, when condensate accumulates within a sealed vessel (not shown), a spring bearing member 115 is also raised along with a rise of the float 108; however, the sub-arm 102 remains at the same position because of the gas outlet valve body 125 of the change-over valve 120 being in the closed position by way of the valve operating rod 111 and actuating rod 121 and because of the fixed pin 106, so that a spring bearing member 116 is pivotally moved and the coil spring 103 is compressed and deformed. The reaction force due to the compression and deformation of the coil spring 103 acts on the pin 110 in such a manner as to cause the sub-arm 102 to be pivotally moved clockwise.
Further rise of the float 108 brings about an agreement of the coil spring 103 with the sub-arm 102 on a straight line. Then, when the position of the spring bearing member 115 further rises and the angle which the coil spring 103 makes with the sub-arm 102 exceeds 180 degrees, the reaction force due to the compression and deformation of the coil spring 103 acts on the pin 110 in such a manner as to cause the sub-arm 102 to be pivotally moved counterclockwise. As a result, the coil spring 103 instantaneously recovers to its original shape, and the connecting portion (pin 110) between the coil spring 103 and the sub-arm 102 is moved down in a snap motion, causing the change-over valve 120 to be drawn downward through the valve-operating rod 111, so that the valve is switched in a short time.
Such a liquid pressure-feeding device enables liquid to be fed under pressure with a simple construction and a better efficiency. However, the pin 107, with which the valve actuating rod 111 is attached, can be easily damaged.
Namely, since in the conventional liquid pressure-feeding device the valve operating rod 111 is adapted to be moved up and down with the pin 106 as a fulcrum for its pivotal movement, the turning moment (torque) acts on the parts of the pin 106 and fitting pin 107 every time there is a snap switching operation and is subjected to wear.
Further, the change-over valve 120 is of such a construction that when one of the valve parts of the gas inlet and outlet valve mechanism is closed, the other valve part is opened, and as understood from the relationship in the position of both valve parts 122, 123 and the actuating rod 121 in FIG. 6, the actuating rod 121 can not be subjected to a shock along the center axis of the actuating rod 121 at the time of the switching operation of the change-over valve 120, but the actuating rod 121 and, therefore, the valve operating rod 111 act to rotate the axis thereof relative to the fitting pin 107. As a result, the pin 107 and the valve operating rod 111 are not brought into uniform contact with each other, and therefore, the pin 107 is subjected to bias wear and is damaged.
When wear of the pin 106 is increased and the pin 107 is damaged, switching of the change-over valve 120 can not be ensured and liquid can not efficiently be fed under pressure.